former navy s.e.a.l. chris kyle who claimed a record 150 kills in iraq died at the hands of another vet, authorities say, allegedly using a semiautomatic handgun. what police don't know yet is why. >> i don't know that we'll ever know. he's the only one that knows that. but at this point he hasn't made any comments to law enforcement as to why he did it. >> they all drove together in a pickup truck, authorities say. less than two hours later, kyle and littlefield were dead. ralph had fled to his sister's house. he told her what happened. she called police. and ralph was eventually caught. ralph is an iraq war veteran. he left the marines in 2010. kyle, who wrote the best-selling auto biography "american sniper" talked about the duty to those he served with in an interview with kttv last year. >> my only regret are the ones i couldn't save. >>> he started a foundation to help those suffering from ptsd. that may be why kyle and littlefield went to the gun range with ralph. >> mr. kyle works with people suff